TY - JOUR
T1 - Confined Water Cluster Formation in Water Harvesting by Metal–Organic Frameworks: CAU-10-H versus CAU-10-CH3
AU - van der Veen, Monique A.
AU - Canossa, Stefano
AU - Wahiduzzaman, Mohammad
AU - Nenert, Gwilherm
AU - Frohlich, Dominik
AU - Rega, Davide
AU - Reinsch, Helge
AU - Shupletsov, Leonid
AU - Markey, Karen
AU - De Vos, Dirk E.
AU - Bonn, Mischa
AU - Stock, Norbert
AU - Maurin, Guillaume
AU - Backus, Ellen H.G.
N1 - Accession Number: WOS:000974367700001
PubMed ID: 36651201
PY - 2024/3/21
Y1 - 2024/3/21
N2 - Several metal–organic frameworks (MOFs) excel in harvesting water from the air or as heat pumps as they show a steep increase in water uptake at 10–30 % relative humidity (RH%). A precise understanding of which structural characteristics govern such behavior is lacking. Herein, CAU-10-H and CAU-10-CH3 are studied with -H, -CH3 corresponding to the functions grafted to the organic linker. CAU-10-H shows a steep water uptake ≈18 RH% of interest for water harvesting, yet the subtle replacement of -H by -CH3 in the organic linker drastically changes the water adsorption behavior to less steep water uptake at much higher humidity values. The materials’ structural deformation and water ordering during adsorption with in situ sum-frequency generation, in situ X-ray diffraction, and molecular simulations are unraveled. In CAU-10-H, an energetically favorable water cluster is formed in the hydrophobic pore, tethered via H-bonds to the framework μ-OH groups, while for CAU-10-CH3, such a favorable cluster cannot form. By relating the findings to the features of water adsorption isotherms of a series of MOFs, it is concluded that favorable water adsorption occurs when sites of intermediate hydrophilicity are present in a hydrophobic structure, and the formation of energetically favorable water clusters is possible.
AB - Several metal–organic frameworks (MOFs) excel in harvesting water from the air or as heat pumps as they show a steep increase in water uptake at 10–30 % relative humidity (RH%). A precise understanding of which structural characteristics govern such behavior is lacking. Herein, CAU-10-H and CAU-10-CH3 are studied with -H, -CH3 corresponding to the functions grafted to the organic linker. CAU-10-H shows a steep water uptake ≈18 RH% of interest for water harvesting, yet the subtle replacement of -H by -CH3 in the organic linker drastically changes the water adsorption behavior to less steep water uptake at much higher humidity values. The materials’ structural deformation and water ordering during adsorption with in situ sum-frequency generation, in situ X-ray diffraction, and molecular simulations are unraveled. In CAU-10-H, an energetically favorable water cluster is formed in the hydrophobic pore, tethered via H-bonds to the framework μ-OH groups, while for CAU-10-CH3, such a favorable cluster cannot form. By relating the findings to the features of water adsorption isotherms of a series of MOFs, it is concluded that favorable water adsorption occurs when sites of intermediate hydrophilicity are present in a hydrophobic structure, and the formation of energetically favorable water clusters is possible.
KW - metal–organic frameworks
KW - sum-frequency generation
KW - water clusters
KW - water harvesting
UR - http://www.scopus.com/inward/record.url?scp=85153097672&partnerID=8YFLogxK
U2 - 10.1002/adma.202210050
DO - 10.1002/adma.202210050
M3 - Article
AN - SCOPUS:85153097672
SN - 0935-9648
VL - 36
JO - Advanced Materials
JF - Advanced Materials
IS - 12
M1 - 2210050
ER -